1. Field of the Invention
The present invention relates to a permanent magnet alloy material and, more particularly, to a multi-component rare earth magnet alloy belonging to 2-17 type Sm-Co magnets among rare earth magnet alloys.
2. Description of the Prior Art
Permanent magnets are generally utilized for various apparatus such as rotational appliances, and communication, measuring and acoustic apparatus. It is desirable that a permanent magnet has great residual magnetic flux density (Br), coercive force (Hc) and maximum magnetic energy product (BHmax) respectively and can stably maintain magnetic property. Since a predetermined level of magnetic fields can be obtained with a small volume by using a magnet of greater maximum magnetic energy product (BHmax), it is possible to reduce the size and the weight of the appliances.
At the initial stage of using KS steels for permanent magnet material, Alnico magnetic and ferrite magnet have been used long since and, owing to the subsequent study for the rare earth magnets and the development of SmCo.sub.5 sintered magnets, the maximum energy product of the magnet has been improved outstandingly. SmCo.sub.5 is referred to as a 1-5 type magnet, which is an intermetallic compound present in Sm-Co binary series and it has a saturation magnetic flux density (Bs) as high as 9.0 KG and the maximum energy product of up to 20 MGOe.
Then, an earnest effort has been made for the development of magnets having more excellent magnetic property than SmCo.sub.5, and rare earth magnets utilizing a Sm.sub.2 Co.sub.17 compound having Bs value of as high as 12.8 KG has been developed. The magnets of this type are collectively referred to as a 2-17 type magnet which are rare earth magnets typically represented by Sm (Co, Fe, Cu).sub.6.8 and Sm (Co, Fe, Cu, Zr).sub.7.4, which have high maximum energy product (BHmax) of about 30 MGOe and intrinsic coercivity iHc of greater than 10 KOe.
However, Sm in the rare earth metal is expensive and the resource therefor has almost been drained and, accordingly, it is difficult to be available. In view of the above, for obtaining inexpensive magnets, it has been proposed rare earth magnets in which Sm in the conventional rare earth magnet is partially substituted with Nd, Ce and Pr which are abundant in view of the resource. The magnets have the maximum energy product of about 24 MGOe and the coercive force bHc of 7.6 KOe (iHc of about 9 KOe: JPA No. 62-243731, Official Gazette), and both of the maximum energy product and the coercive force are lower than those of Sm-Co-Fe-Cu-Zr alloy, multi-component rare earth alloy belonging to Sm-Co magnets.
Further, with the same reason, it has also been proposed a rare earth magnet in which Sm is partially substituted with Ce and further incorporated with Zr and B. The proposed magnet has the maximum energy product of about 24 MGOe and the coercive force iHc of about 13 KOe (JPA No. 63-28844, Official Gazette). However, it has not yet been produced and marketed. As commercially available magnet of SiCe series, it has only been put to practical use of those having the maximum energy product of about 22 MGOe and the coercive force iHc of about 9 KOe and both of the maximum energy product and the coercive force are lower as compared with those of Sm-Co-Fe-Cu-Zr series alloys. It is supposed to be attributable to the difficulty in view of the production such as sintering property. Accordingly, in rare earth magnet alloys, it has been desired that they are inexpensive and have large coercive force and maximum energy product.
However, when it is intended to obtain an inexpensive rare earth magnet alloy by substituting expensive Sm with Nd, Ce, etc. which are abundant in view of natural resource, it is only possible to produce those having the maximum energy product of at most about 2 MGOe and the coercive force iHc of about 9 KOe as has been described above in the patent literature.